Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 19 peer-reviewed journal articles Updated
Neurology · Primary Angiitis of the Central Nervous System

Understanding Your Diagnosis: Primary Angiitis of the Central Nervous System

At a Glance

PACNS is a rare condition in which the immune system inflames blood vessels in the brain and spinal cord. A brain biopsy gives the most specific evidence, but blood-vessel imaging and clinical findings can support diagnosis when inflammation is patchy or biopsy is unsafe.

Receiving a diagnosis like Primary Angiitis of the Central Nervous System (PACNS) can be overwhelming, especially because the name is rarely heard outside of specialized medical circles. It is common for local doctors or even general neurologists to have never treated a case personally, as the disease is exceptionally rare [1]. Understanding what is happening inside your body is the first step toward managing the road ahead.

Defining the Condition

Primary Angiitis of the Central Nervous System (PACNS) is an umbrella term for a rare condition where the immune system mistakenly attacks the blood vessels within the brain and spinal cord [2][3].

You may hear the older term granulomatous angiitis. Historically, this was used as a specific name for the disease, but today it is recognized as just one of the three main “patterns” of inflammation seen under a microscope during a biopsy [2]. The three patterns are:

  • Granulomatous: Characterized by specialized immune cells forming small clusters called granulomas [4]. This is found in about 32% to 61% of biopsied cases [5].
  • Lymphocytic: Where the inflammation is dominated by white blood cells called lymphocytes [2].
  • Necrotizing: Where the inflammation causes necrosis, or tissue death, in the vessel wall [2]. This pattern’s specific meaning for your outlook will be interpreted by your doctor alongside your symptoms.

Regardless of which pattern is found, the goal of treatment remains focused on calming the inflammation to protect your brain tissue.

A Targeted Attack

It is important to understand that PACNS is strictly limited to the Central Nervous System (CNS), which includes the brain, spinal cord, and the leptomeninges (the thin layers of tissue covering the brain) [6][7].

This is different from “systemic” vasculitis, such as Granulomatosis with Polyangiitis (GPA), which can affect the lungs, kidneys, and other organs throughout the body [6]. In PACNS, your medical team will conduct a systematic search (such as checking your lungs, sinuses, and kidney function) to evaluate for signs of systemic disease. Having a lung issue doesn’t automatically mean you don’t have PACNS, but it prompts doctors to look closely for systemic vasculitides that can also involve the brain [8].

What is Happening to the Blood Vessels?

The core of the disease is transmural inflammation. This means that inflammatory cells have moved into and through the entire thickness of the blood vessel wall, rather than just sitting on the surface [9][10].

This internal attack causes several problems:

  1. Vascular-Wall Damage: The structure of the blood vessel becomes weak or scarred [9].
  2. Narrowing (Stenosis): As the walls swell with inflammation, the space where blood flows gets smaller [11].
  3. Reduced Blood Flow (Ischemia): When vessels narrow or become blocked by tiny clots (thrombosis), the brain tissue downstream may not get enough oxygen, which can lead to injury [12].

A Rare Road

PACNS is extremely rare. Estimates suggest it affects approximately 2.4 to 5.1 people per million every year [1][13]. Because it is so uncommon, it is normal to feel isolated or like your diagnosis is a medical mystery.

Diagnosis often utilizes a brain biopsy—a procedure where a tiny piece of brain or meningeal tissue is removed for examination—as it provides the most specific evidence that the inflammation is truly within the vessel walls and not caused by an infection or a different condition [9][14]. Because the disease can be “patchy” (affecting some vessels while skipping others nearby), a biopsy can sometimes be negative even when the disease is present [15][16]. In these cases, or when a biopsy isn’t safe, doctors rely on an integrated synthesis of detailed imaging like angiography (a specialized X-ray of the blood vessels) alongside your clinical symptoms to support the diagnosis [17][18].

While the cause of this immune “wrong turn” is not yet fully understood, modern medicine provides clear pathways for treating the inflammation and protecting the brain from further damage [19][5].

Common questions in this guide

What is primary angiitis of the central nervous system (PACNS)?
PACNS is a rare condition in which the immune system inflames the blood vessels in the brain and spinal cord. The inflammation can damage or narrow those vessels and reduce blood flow to nearby nervous tissue.
Does granulomatous angiitis mean something different from PACNS?
Granulomatous angiitis is an older name that was used for PACNS. Today, granulomatous usually describes one of three inflammation patterns that may be seen in a biopsy, along with lymphocytic and necrotizing patterns.
How do doctors diagnose PACNS?
A brain or meningeal biopsy can provide the most specific evidence that inflammation is inside the vessel walls and is not due to an infection or another condition. Because PACNS can affect some vessels but spare nearby ones, a biopsy may be negative even when the disease is present. If a biopsy is unsafe or does not settle the diagnosis, doctors combine angiography, symptoms, and other clinical findings.
What does a granulomatous pattern on a PACNS biopsy mean?
It means specialized immune cells have formed small clusters called granulomas in the inflamed tissue. It is one of three recognized patterns, and your doctor interprets its significance alongside your symptoms and other test results.
How is PACNS different from systemic vasculitis?
PACNS is limited to the central nervous system, including the brain and spinal cord. Systemic vasculitis can affect other organs, such as the lungs, sinuses, or kidneys, as well as the nervous system. Doctors check for signs outside the nervous system to distinguish these conditions.
What does transmural inflammation mean in PACNS?
Transmural inflammation means inflammatory cells extend through the full thickness of a blood vessel wall. This can weaken or scar the wall, narrow the passage for blood, and reduce blood flow; small clots can also contribute to blockage.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my tests, do I have 'biopsy-confirmed' or 'imaging-supported' PACNS?
  2. 2.Was a granulomatous pattern found in my biopsy, and how does that specific pattern affect my outlook?
  3. 3.How did you systematically rule out systemic vasculitis or other conditions that can look like PACNS?
  4. 4.Given the rarity of this condition, are you collaborating with a specialized vasculitis center or a neuro-rheumatologist?
  5. 5.Can you walk me through the 'transmural inflammation' seen in my results and what it means for my brain's blood flow?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (19)
  1. 1

    Primary angiitis of the central nervous system presenting as a mass lesion.

    Gan C, Maingard J, Giles L, et al.

    Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 2015; (22(9)):1528-31.

    PMID: 26119979
  2. 2

    Pathology of Primary Angiitis of the Central Nervous System.

    Siala S, Rahoui N, Cho B, Zamora CA

    Neuroimaging clinics of North America 2024; (34(1)):31-37 doi:10.1016/j.nic.2023.06.002.

    PMID: 37951703
  3. 3

    Primary Angiitis of the Central Nervous System.

    Mandal J, Chung SA

    Rheumatic diseases clinics of North America 2017; (43(4)):503-518 doi:10.1016/j.rdc.2017.06.001.

    PMID: 29061238
  4. 4

    Granulomatous Angiitis of the Central Nervous System Associated with Hodgkin's Lymphoma: Case Report and Literature Review.

    Lopez-Chiriboga AS, Yoon JW, Siegel JL, et al.

    Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association 2018; (27(1)):e5-e8 doi:10.1016/j.jstrokecerebrovasdis.2017.08.029.

    PMID: 28943218
  5. 5

    Overview of Primary Angiitis of the Central Nervous System: Current Insights.

    Phu A, Agrawal DK

    Archives of internal medicine research 2026; (9(1)):40-52 doi:10.26502/aimr.0236.

    PMID: 41947889
  6. 6

    Central Nervous System Vasculitis: Primary Angiitis of the Central Nervous System and Central Nervous System Manifestations of Systemic Vasculitis.

    Amin M, Uchino K, Hajj-Ali RA

    Rheumatic diseases clinics of North America 2023; (49(3)):603-616 doi:10.1016/j.rdc.2023.03.011.

    PMID: 37331735
  7. 7

    Primary angiitis of the central nervous system: avoiding misdiagnosis and missed diagnosis of a rare disease.

    Bhattacharyya S, Berkowitz AL

    Practical neurology 2016; (16(3)):195-200 doi:10.1136/practneurol-2015-001332.

    PMID: 26837371
  8. 8

    [Primary central nervous system vasculitis].

    Schuster S, Magnus T

    Zeitschrift fur Rheumatologie 2015; (74(10)):854-6, 858-60, 862 doi:10.1007/s00393-015-0007-9.

    PMID: 26589203
  9. 9

    Primary Angiitis of the Central Nervous System and Its Mimics: A Pattern-Based Approach to Biopsies for Central Nervous System Vasculitis.

    Cecchi R, Becker N, Conway KS

    Archives of pathology & laboratory medicine 2025; (149(10)):e315-e322 doi:10.5858/arpa.2024-0286-RA.

    PMID: 40079061
  10. 10

    A case of unexpected death due to primary angiitis of the central nervous system.

    Yang L, Zheng Z, Zeng Y, et al.

    Forensic science, medicine, and pathology 2024; (20(2)):675-680 doi:10.1007/s12024-023-00631-4.

    PMID: 37126199
  11. 11

    Primary Angiitis of the Central Nervous System: An Uncommon Cause of Stroke in the Young.

    Thekkekarott Kuruvila A, Ranawat N, Hegde N, Arora A

    Cureus 2022; (14(8)):e27799 doi:10.7759/cureus.27799.

    PMID: 36106213
  12. 12

    The Hemorrhagic Side of Primary Angiitis of the Central Nervous System (PACNS).

    Zedde M, Napoli M, Moratti C, et al.

    Biomedicines 2024; (12(2)) doi:10.3390/biomedicines12020459.

    PMID: 38398061
  13. 13

    Primary Angiitis of the Central Nervous System: A Medical Mystery.

    Robert S, Deepica R, Arpitha K, Wilson C

    Romanian journal of internal medicine = Revue roumaine de medecine interne 2026; doi:10.2478/rjim-2026-0017.

    PMID: 42557804
  14. 14

    Diagnostic Yield and Safety of Brain Biopsy for Suspected Primary Central Nervous System Angiitis.

    Torres J, Loomis C, Cucchiara B, et al.

    Stroke 2016; (47(8)):2127-9 doi:10.1161/STROKEAHA.116.013874.

    PMID: 27354225
  15. 15

    Extended stereotactic brain biopsy in suspected primary central nervous system angiitis: good diagnostic accuracy and high safety.

    Stoecklein VM, Kellert L, Patzig M, et al.

    Journal of neurology 2021; (268(1)):367-376 doi:10.1007/s00415-020-10157-2.

    PMID: 32813052
  16. 16

    Primary Angiitis of the Center Nervous System: A Clinical Challenge Diagnosed Postmortem.

    Al Share B, Zakaria A, Hiner E, et al.

    Case reports in neurological medicine 2017; (2017()):3870753 doi:10.1155/2017/3870753.

    PMID: 28758039
  17. 17

    Subtypes of primary angiitis of the CNS identified by MRI patterns reflect the size of affected vessels.

    Schuster S, Bachmann H, Thom V, et al.

    Journal of neurology, neurosurgery, and psychiatry 2017; (88(9)):749-755 doi:10.1136/jnnp-2017-315691.

    PMID: 28705900
  18. 18

    Primary angiitis of the central nervous system as a mimic of multiple sclerosis: A case report.

    de Souza Tieppo EM, da Silva TFF, de Araujo RS, et al.

    Journal of neuroimmunology 2022; (373()):577991 doi:10.1016/j.jneuroim.2022.577991.

    PMID: 36356513
  19. 19

    Immune cell profiling in the cerebrospinal fluid of patients with primary angiitis of the central nervous system reflects the heterogeneity of the disease.

    Strunk D, Schulte-Mecklenbeck A, Golombeck KS, et al.

    Journal of neuroimmunology 2018; (321()):109-116 doi:10.1016/j.jneuroim.2018.06.004.

    PMID: 29957380

This page is for informational purposes only and does not constitute medical advice. Your neurologist, rheumatologist, or other specialist should interpret your PACNS tests and discuss your care.

Get notified when new evidence is published on granulomatous angiitis.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.